SCP-258

Item #: SCP-258

Object Class: Euclid

Special Containment Procedures: A Foundation-operated surveillance system is to be maintained on SCP-258. SCP-258 is located in the town of ██████, approximately 30 miles south of ███████████, in southwestern Missouri. A covert entrance to the tunnel (referred to as Site-██) is situated under a two-story restaurant near the point where Interstate 44 crosses over the river at ██████. The entrance is disguised as an abandoned mine shaft, and is disguised with a layer of tarp. The subterranean area surrounding Site-██ has been modified to replicate hidden back roads and railroad tracks on the riverbed.

A minimum of 10 security personnel are to monitor Site-258 on a 24 hour basis. Any subjects approaching or exiting SCP-258 are to be intercepted and detained until further notice.

Description: SCP-258 is a covered, circular tunnel approximately 18 meters in diameter. The tunnel passes through solid bedrock and has been in continuous use, with little maintenance, since its initial discovery in the 1920s. The tunnel's passage can be illuminated by artificial light sources without compromising structural integrity or causing damage to the subterranean area.

When one or more subjects enter SCP-258, they note that sounds of various mechanical and electrical systems echo throughout the tunnel at seemingly random intervals. Subjects are able to navigate the tunnel unscathed despite experiencing these sounds as loud and distracting, and without perceiving their source. These sounds will cease once subjects exit SCP-258 or enter a sealed facility. Extensive surveillance of the tunnel has failed to reveal any signs of its anomalous effect.

SCP-258 was first discovered during the construction of Interstate 44 in the early 1970s, when Foundation Agents discovered an abandoned freight train in an underground tunnel hidden beneath the highway. After receiving authorization to open a site beneath the railroad tracks to prevent it from falling into disrepair, Agents reopened Site-██ as an alternate route for transportation between Shreveport, LA and Los Angeles, CA. Current containment procedures were implemented shortly thereafter.

Addendum 258-01: After further study, it has been determined that the sound of the train is not anomalous. Instead, the sounds are most likely the result of a normal train engine operating in an underground tunnel. The sound of a freight train is consistent with other known abandoned train tunnels, including those under the Hoover Dam and Deep Lake, CO.